Prior to the present invention a variety of heterogeneous catalysts have been reported in the literature for oxidation of various organic compounds with gaseous oxygen. For example, an ion-exchanged transition metal catalyst, such as a sulfonic acid-type resin having valence bonded rhodium and vanadium has been disclosed in U.S. Pat. No. 4,021,369 for the oxidation of olefins to epoxy alcohols with gaseous oxygen.
The use of palladium, rhodium or cobalt supported on alumina for tetralin oxidation has been described by A. V. Artimor et al, Russian J. Phys. Chem., 51 (4), 576-7, 1977. However, the selectivity of 1-tetralone is poor with these catalysts.
Heterogeneous catalysts have also been claimed for the liquid-phase oxidation of tetralin as reported in Israeli Pat. No. 41114. High 1-tetralone to 1-tetralol ratios are obtained using a specially prepared insoluble chromium oxide catalyst along with a heterocyclic amine. The catalyst preparation is an involved process and the fine powdery nature of the catalyst could lead to plugging problems in the reactor. Good agitation is needed for the catalyst to be available in the entire reaction zone and hence, packed beds are not very suitable for these gas-liquid reactions.
In contrast, most of the difficulties and disadvantages of the known methods have been overcore by the present invention. The use of the metal exchanged catalyst along with a heterocyclic aromatic amine modifier gives yields and efficiencies comparable to or better than those when the same metals are used in homogeneous form. The metal ion exchanged catalyst is easily prepared by a very simple process using commercially available ion-exchange resins and metal salts and does not necessitate the use of high temperatures.
Accordingly, one or more of the following objects will be achieved by the practice of this invention. It is an object of this invention to provide an improved liquid-phase process for the oxidation of tetralin to tetralone. Another object of this invention is to provide an improved process for the oxidation of tetralin in the presence of a novel metal exchanged cation-exchange resin catalyst. A further object of the invention is to provide a process which utilizes chromium III exchanged on a gelular carboxylic acid-type resin. Another object of this invention is to provide a liquid-phase oxidation of tetralin to 1-tetralone with gaseous oxygen in the presence of a chromium exchanged cation-exchange resin catalyst and an aromatic amine catalyst-modifier. These and other objects will readily become apparent to those skilled in the art in the light of the teachings herein set forth.